The present invention relates generally to internal combustion engines, and more particularly, to an internal combustion engine utilizing a rotary valve for directing the flow of intake air into the cylinders and exhausting gases from the cylinders.
Increasing concerns about the impact of the internal combustion engine on global warming are putting added pressures on the automotive industry to develop more environmentally friendly engines. Generally, the approach is to increase the fuel economy of the engine by reducing the displacement in efforts to burn less fuel. This small displacement engine would be used as a stand alone power plant or as the principal source of power in an electric hybrid configuration. Currently, the most promising approach is to use the most efficient internal combustion engine, the direct injection diesel, and reduce its displacement to as small as operationally possible. It is in this application and as a small cylinder displacement stand alone power source that the Rotary Valve Diesel (RVD) is expected to be particularly well suited.
Previous art on the RVD attempted to reduce emissions by using the same strategy used decades ago with the Otto gasoline engine to increase fuel economy. Thus, as stated above, the displacement of the engine was decreased in an effort to burn less fuel per mile which also would result in reduced emissions. However, this small displacement engine would encounter the same problem as with the Otto engines, namely, reduced output. The RVD again used the same strategy of increasing rpms"" to increase output as was done earlier with the Otto engine. Also, some modest increase in efficiency due to improved thermodynamic and volumetric efficiency would add to this output. This increased power would increase consumer acceptance of the engine and with that, both fuel consumption and emissions would decrease.
While the RVD exhibits many advantages over conventional diesels when attempting to build small cylinder displacement engines, it still does not dramatically reduce either emissions or the characteristic diesel noise associated with thexe2x80x94fast burn phase of combustion in comparison to conventional diesels of similar displacements. The diesel noise is potentially problematic because of consumer aversion to this condition.
The art now presented makes major improvements in the reduction of both noise and emissions as well as reductions in cost while increasing durability. A new feature, the Peak Pressure Reducing Valve (PPRV), can reduce or prevent the spike in pressure and temperature by opening a valve during the rapid burn phase of the combustion cylinder and instantly transfer this heat and pressure to the compression cylinder. First, this reduces noise and second it reduces NOx. The PPRV reduces NOx by preventing its creation and performs like an EGR system allowing for the reduction of any NOx that is produced.
The PPRV also reduces HC emissions. HC emissions are produced by incomplete burning in crevice spaces. Most of the crevice spaces in the RVD are located above the piston, around the seals, and above the top most piston ring. Being that the combustion bowl is off center and the opening for the PPRV is at the point located in the seals closest to the center of the engine, the area of greatest concentration of HC emissions is this very same area from which the combustion gas is drawn while the piston is still relative close to the valve. These gases are passed to the cylinder in the compression cycle to become part of the charge to be burned during the next combustion cycle.
Also reducing NOx is the cooled EGR system located on the rotary valve. Adding to reduced emissions is the cooling of the intake charge by the cooling fins placed on the valve housing. A second benefit of cooling the intake charge is an improvement in volumetric efficiency.
Also increasing efficiency is the PPRV. Thermal efficiency should be improved due to the mixing of gas in both the compression and combustion cycle cylinders ultimately creating more complete combustion. This mixing is due to the very rapid exit of gas from the combustion cylinder and injection into the compression cylinder creating turbulence in both cylinders. Another feature increasing efficiency is the thermal transfer plate which transfers heat via conduction from the power stoke to the compression stroke. Both the PPRV and the thermal transfer plate are positioned not to operate until the intake is fully closed. Heat energy is now added to the compression cycle by both elements. This added heat energy is then present at the beginning of the combustion cycle allowing more reliable and quicker ignition. This is especially important as cylinder displacement is reduced and would allow the RVD to operate in cylinder displacements smaller than conventional diesel engines.
Finally, the last two features increase durability. First, the valve shape is changed to a more xe2x80x9cbellxe2x80x9d shaped configuration and made smaller making it stronger. Lastly, the seal system is changed adding a double piston type seal around the valve. This in combination to the seals on the block allow the double sealing of the initial 60% to 65% of the power stroke.
The last point to be addressed is the use of ceramics or ceramic coatings on the RVD. While this technology can also be used on conventional engines, it should be less costly when used on the RVD. This would be due to fewer parts being affected and the parts affected being relatively easy to coat. In the RVD the same exhaust serves several cylinders and therefore has more heat available to burn soot. This effect can be increased at relatively low cost by coating the exhaust with ceramics."" An additional benefit of this coating would be less heat transferred to the intake charge. Similarly, a ceramic coating on the bottom of the valve would also reduce heat transfer and increase the durability of the valve. Coating both of these elements would be the start of making the RVD a low heat rejection engine.
All the improvements of the RVD are intended to allow a small cylinder displacement diesel to replace the Otto gasoline engines of the same power. The RVD could be used in the preferred embodiment of one rotary valve serving four cylinders or in engines having multiples of four cylinders. Potential markets would include light auto and truck, outboard marine, motorcycles, and light aircraft to name a few. However, given that the RVD appears to have significant emissions and noise advantages, it would be expected that the RVD technology would be applied to Diesels of ever increasing cylinder displacement engines. Therefore the potential market for the RVD is huge. Correspondingly, the potential for fuel savings and reduction in emissions and greenhouse gases is very significant.
The present invention is an internal combustion engine having at least one cylinder. A rotary disk valve is located over the top of the cylinders for rotation about an axis parallel to the axis of the cylinders. The center of each cylinder is equally spaced from the axis of rotation of the rotary disk valve. The valve includes an intake passage for directing intake air into the cylinders and an exhaust passage for exhausting combustion gases from the cylinders. The intake passage and exhaust passage in the rotary valve communicate with each cylinder in succession as the valve rotates, allowing the use of a single valve to serve multiple cylinders. The rotary valve uses piston type seals to prevent the movement of gas from the cylinders past the valve. This valve seal is well lubricated by an oil nozzle to produce a tight seal with minimal friction. Another set of seals is located around the major portions of the tops of each cylinder to prevent the movement of engine gases between cylinders.
In another aspect of the engine, the intake and exhaust valve openings as well as the intake and exhaust passages are increased in size by at least 40% over conventional poppet valve engines. This not only increases pumping efficiency, but also allows the air transport capacity to be increased from at least double to as much as four times that of conventional engines.
While the rotary valve engine herein described could use various fuels, the preferred fuel would be diesel. As such, the rotary valve engine as described, is referred to as the Rotary Valve Diesel (RVD) and further comparisons to conventional engines will be inferred to be poppet valve diesel Engines.
Another feature of the RVD shapes the intake and exhaust valve openings of the valve to minimize valve overlap while maximizing valve opening areas. This allows the engine to be kept very compact without compromising pumping efficiencies. Further, the openings can be shaped to allow the RVD to double seal the first 60 to 65% of the power stroke increasing the RVD""s sealing capacity.
The RVD uses twin counter rotating crankshafts in engine configurations of four cylinders and larger. This four cylinder configuration or multiples of this format are the preferred embodiment of this engine. In the four cylinder, this configuration requires that each crankshaft have two crank throws which are adjacent and 180 degrees apart. Each crankshaft has gears attached to it which mesh together to synchronize the crankshafts and transfer power to the crankshaft with the flywheel attached to it. The other crankshaft has a gear on it to drive the valve. This arrangement is very effective in reducing vibration with minimal counter weighting and produces high torque.
The crank throws of each crankshaft overlap as they rotate. This is possible because the crank throws of opposing crankshafts rotate 180 degrees out of phase. The use of this feature allows the cylinders to be placed closer together, thereby making the engine more compact.
The RVD uses several elements to reduce emissions. The most dramatic element is the use of the Peak Pressure Reducing Valve (PPRV). The PPRV is located on the rotary valve and has an intake timed to open at the beginning of the fast burn phase of combustion with the intent of minimizing or preventing the rapid spike in temperature and pressure. The PPRV closes at what would be the end of this normally occurring spike. The PPRV opening transfers gas through a passage located in the rotary valve from this high pressure area to a lower pressure area, the compression cylinder. PPRV opening is sized to only allow enough gas to be transferred from the combustion stroke to the compression stroke to smooth out the pressure and temperature rise. Since the combustion temperature is reduced, NOx emissions are reduced. Also, as the gas escapes from the combustion cylinder, it should take much of the gas caught in the crevice space above the piston and transfer this gas to the compression cylinder to then be burned when this cylinder enters its"" own combustion cycle. Since crevice spaces are responsible for increased HC emissions, this should reduce HC emissions. Finally, soot also is reduced due to the rapid exit of gas from the combustion cylinder and the rapid entrance into the compression cylinder causing increased turbulence in both cylinders resulting in more complete combustion in the combustion cycle. Further soot reductions could be made by coating the inside surface of the exhaust with ceramics.
Another key benefit of the PPRV is the also related to reducing the pressure and temperature spike in the combustion cycle. This is the reduction of the noise produced by this event. As this is a major consumer complaint, reducing and possibly eliminating this noise would make the RVD much more attractive to consumers.
The final benefit of the PPRV is its"" ability to transfer heat energy to the compression cycle. This heat is transferred as the hot gas moves through the PPRV to the compression cylinder. More heat energy is transferred from the combustion cycle to the compression cycle by the Thermal Transfer Plate. This device is simply a plate made.
It should be noted that the EGR should also reduce HC emissions. This is due to the EGR intake picking up any trapped gas from between the cylinders as it rotates from one to the next. HC rich gas could be present in this area if the seals experience any leakage during the combustion cycle.
The last new feature, is the cooling of the valve housing. Cooling fins are added to the valve housing to cool the intake charge contained within it. Being that the surface area of the valve housing is quite large, it provides ample opportunity to cool the intake air. In addition, a conventional intercooler could also be used to further cool the intake charge.
Based on the foregoing, it is a primary object of the present invention to provide a rotary valve engine which has lower emissions than conventional poppet valve engines.
Another object of the present invention is to provide a rotary valve engine which exhibits lower noise, vibration and harshness than conventional poppet valve engines.
Still another object of the present invention is to provide a rotary valve engine which has both greater pumping efficiencies and air transport capacities as compared to conventional poppet valve engines.
Yet another object of the present invention is to provide a rotary valve engine which has greater thermal efficiencies than conventional poppet valve engines.
Another object of the present invention is to provide a rotary valve engine which is more compact and lightweight than conventional poppet valve engines.
Still another object of the present invention is to provide a rotary valve engine which will increase the rpms compared to conventional poppet valve engines.
Yet another object of the present invention is to provide a rotary valve engine which will increase the power to weight ratio as compared to conventional poppet valve engines.
Another object is to provide a rotary valve engine which is relatively inexpensive to produce.
Still another object of the present invention is to provide a rotary valve engine which is very reliable.
Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and accompanying drawings which are merely illustrative of such invention.